Method for varnishing leather and like material



Patented Dec. 31, 1929 PATENT OFFICE JEAN PAISSEA'U, OF PARIS, FRANCE mn'rnon r012. vanmsnme LEATHER. AND LIKE "MATERIAL I fo Drawing. Application filed October 19, 1925, Serial No. 63,569, and in France July 23, 1925.

The'products in current use for the varnishing of leather and like material of animal or vegetable orlgm COIlSlSt' of complex coatlngs which are diflicult of application and dry at 1 5 a slow rate, such products always containing linseed oil which is variously treated with gums or resinous substances. Such varnishes are quite adhesive, but they can only be applied in thick layers, thus entirely concealing the underlying leather to which they give the uniform appearance of oil cloth.

It is further observed that a cellulose varnish of the known type, i. e. based upon the use of nitrocellulose or acetate of cellulose dissolved in the usual solvents, with or without the addition of a substance conferring plasticity, will not adhere to leather, and this is due to two reasons.

Firstly, the close grain of the cutaneous derm constituting the leather will cause it to act as'a semipermeable membrane, so that vwhen'the varnish is applied, the solvents alone will penetrate into the leather and the cellulose will not infiltrate between the fibres but will remain on the surface in the shape of a film which fits closely upon all the reliefs but cannot adhere for lack of penetrating roots.

Secondly, the nitrocellulose or acetate of cellulose cannot adhere to the conjunctive fibre of the leather from the fact that cellulose and' its derivatives will not moisten the fibre. There is so to speak an incompatibility between these two substances, so that the nitrocellulose varnish will become detached when the leather is bent or worked up or when is immersed in water.

' to wood, horn and like material.

For this purpose, the invention essentially consists in treating the leather so as'to change the nature of its surface whereby it will become united to the nitrocellulose of the varnish. I treat the leather for instance by a 4 action. I prefer to employ a volatile acid so as to avoid an excessively long action which would attack the leather at a too great depth and would thus reduce its strength in a prejudicial manner.

Among the acids which are preferable for this use, I may mention the following organic acids: acetic, formic, lactic, tartaric, oxalic and like acids, or all other acids or bodies having an acid function, even if they are not miscible with the cellulose varnish, provided they will gelatinize the collagenic fibres of the leather. The varnishing process is carried out in two stages; firstly, the preparation of the leather by the acid treatment, and secondly; when the leather is dry, the application of a suitable cellulose varnish.

Obviously the above cited acids may be replacedby any substances which are capable to give acid products by the chemical decomposition, either spontaneous or caused by the different elements which are in presence, that is to say the constituent parts, of the leather and of the varnish.

But-I am enabled to operate in a more .simple manner, and obtain the most approved results by adding the varnish to acetic acid which has the advantage of being a solvent for'nitrocellulose and acetate of cellulose, so that it may be incorporated into the varnish itself, thus simplifying the work, since the leather can be varnished in a single operation and no preliminary preparation. is needed.

In practice, -I find that the simplest and most rapid method consists in the use of a varnish based upon nitrocellulose for instance, and comprising the usual solvents such as methyl amyl, or ethyl acetate, acetone, or the like; the proportion of nitrocellulose may vary according to circumstances between 2 and 6 per cent in order to afford the requisite fluidity.

To this varnish I add as a mordant a sufiicient amount of concentratedv acetic acid, according to the nature of the leather. In order to obtain the necessary suppleness and elasticity, I incorporate a substance conferring plasticity such castor oil or a derivative of the same which is not of a resinous nature, or any other suitable substance conferring plasticity which is of a stable and non-volatile nature.

According to the result to be obtained and the nature of the leather, I apply the varnish two or three times by means of a brush, a small scraper, an atomizer, or the like, and this will impart a brilliant glazed appearance to the leather without changing its aspect or its qualities.

As above stated, a varnish thus composed may be employed with approved results u on wood, orn or the like, and I further 0 tain an improvement which consists in forming upon the article a surface which is of a silky, velvety, lustrous or pearly nature and producing a most agreeable effect, by

incorporating into a varnish a suitable quantity of pearl essence. The resulting effect will vary according to the amount of pearl essence employed, or according to the number of layers of varnish applied, and the material thus treated will constitute a new manufactured product which is susceptible of numerous applications.

Having thus described my process, what I claim as new therein, and my own invention, is:

1. A process for the varnishing of leathers and like substances, consisting in superficially gelatinizing the leather by the action of a suitable acid and in then covering this surlface thus modified with a cellulosie varms 2. Process for the varnishing of the leathers and like substances which consists in gelatinizing the surface of the said leather by the action of a suitable acid and in coating this gelatinized leather with a layer of a. varnish having cellulose ester as a base.

3. Process for the varnishing of the leathers and like substances which consists in gelatinizing the surface of the said leather in applying superficially a suitable acid dilute in a solvent and in then a plying a varnish having cellulose ester as a ase.

4. Process for the varnishing of the leathers and similar substances which consists in gelatinizing the surface of the said leather by applying superficially a suitable acid diluted in a solvent and in then applying a varnish based upon nitrocellulose to whic suitable substances conferring plasticity are added.

5. Process for the varnishing of the leathers and similar substances which consists in applying upon these substances a solution of a volatile acid capable of gelatinizing at least partially the collagenic fibre of the leather, then in applying upon the substances which have been treated in that Way a cellulosic varnish to which a small quantity of acetic acid is added.

6. Process for the varnishing of the leathers and like substances which consists in applying upon these substances a solution of a volatile acid capable of gelatinizing at least partially the collagenic fibre of the leather, then in applying upon the substances which have thus been treated a cellulosic varnish containing acetic acid and plasticizing agent.

In testimony whereof I have hereunto aflixed my signature. JEAN PAISSEAU. 

